Development of a skin colonization model in gnotobiotic piglets for the study of the microbial ecology of meticillin-resistant Staphylococcus aureus ST398

Abstract

Meticillin-resistant Staphylococcus aureus (MRSA) ST398 continues to spread amongst pigs and other domestic animals and man. This highlights the need for models to examine MRSA colonization and investigate control strategies. This study aimed to develop a gnotobiotic pig model and assess the potential of bacterial interference from selected coagulase-negative staphylococci (CNS) against MRSA ST398. Groups of 2-week-old piglets were atraumatically inoculated either with MRSA and/or CNS. Skin and mucosae were swabbed, and bacterial counts compared over a period of 21days. Piglets developed healthily, and bacterial populations increased similarly for both MRSA and CNS until day 32. On day 37, MRSA counts in groups with CNS reduced significantly compared with MRSA alone (P=0·03). The results showed that inoculation of piglet skin with MRSA resulted in spontaneous colonization and that MRSA ST398 has a low pathogenic potential in gnotobiotic piglets. Quantitative bacteriology indicated that initial MRSA colonization was unaffected by concurrent CNS colonization but that interference may occur over a longer period. Gnotobiotic piglets provide a reproducible model suitable for bacterial interference studies, which should be further explored as an alternative to antimicrobials in the control of MRSA.